ML20059A210
| ML20059A210 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 10/18/1993 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9310260257 | |
| Download: ML20059A210 (10) | |
Text
_ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ - ___________
GENuclear Energy lieneret Dect : Compry 175 Curtrer Avenue. San Jne. CA 95125
/
October 18,1993 Docket No.52-001 44' I
s Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal l
Office of the Nuclear Reactor Regulation
Subject:
Submittal Supporting Accelerated ABWR Schedule - If0 3.6.1.6 and Associated Bases U
Dear Chet:
Enclosed find LCO 3.6.1.6 and associated bases for review and comment. This LCO and i
bases incorporated NRC staff and GE agreement reached on October 14,1993.
I Please provide copies of this transmittal to John Monninger and Mark Reinhart.
l Sincerely, 4,,
/ for Jack Fox Advanced Reactor Programs cc:
Alan Beard (GE)
Norman Fletcher (DOE)
Cal Tang (GE) l I
c~
< V087 1
I mun I
9310260257 931018 IO I
PDR ADOCK 05200001
[9 A
PDR Lg
Wetwell-to-Drywell Vacuum Breakers 3.6.1.6 3.6 CONTAINMENT SYSTEMS 3.6.1.6 Wetwell-to-Drywell Vacuum Breakers LCO 3.6.1.6 Eight wetwell-to-drywell vacuum breakers shall be OPERABLE.
AND Eight wetwell-to-drywell vacuum breakers shall be closed.
APPLICABILITY:
MODES 1, 2, and 3.
ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.
One wetwell-to-A.1 Restore one vacuum 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> drywell vacuum breaker breaker to OPERABLE inoperable for
- status, opening.
B.
One wetwell-to-drywell B.1 Close the open vacuum 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> vacuum breaker not breaker.
closed.
C.
Required Action and C.1 Be in MODE 3.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> associated Completion Time not met.
AND C.2 Be in MODE 4.
36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> l
l ABWR TS 3.6-20 10/18/93
1 1
Wetwell-to-Drywell Vacuum Breakers 3.6.1.6 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY l
l l
NOTE-------------------
Not required to be met for vacuum breakers that are open during Surveillances or when performing their l
intended function.
Verify each vacuum breaker is closed.
14 days AND l
Within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after any discharge of steam to the suppression chamber from the safety /
relief valves (S/RVs) or any operation that causes the drywell-wetwell dif ferential pressure to be reduced by 2
2.007 kg/cm d (0.1 psid).
- If position indicating instruments indicate that one or more vacuum breakers are not closed, verify by alternate means that each vacuum braker is closed within the following 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.
SR 3.6.1.6.2 Perform a functional test of each 18 months required vacuum breaker.
SR 3.6.1.6.3 Verify each required vacuum breaker fillly 18 months a
opens at s 0.035 kg/cm d (0.5 psid).
ABWR TS 3.6-21 10/18/93
t Weteell-to-Drywell Vacuum Breakers 3.6.1.6 l
SURVEILLANCE REQUIREMENTS.(continued) i SURVEILLANCE FRE0VENCY SR 3.6.1.6.4 Perform CHANNEL CALIBRATION of vacuum 18 months breaker position indication channel.
E 1
h L
t
.s i
o T
ABWR TS 3.6-22 10/18/93 J
4 Wetwell-to-Drywell Vacuum B 3.6.1.6 B 3.6 CONTAINMENT SYSTEMS B 3.6.1.6 Wetwell-to-Drywell Vacuum Breakers BASES BACKGROUND The function of the wetwell-to-drywell vacuum breakers is to relieve vacuum in the drywell. There are 8 internal vacuum breakers between the drywell and the wetwell, which allow gasland steam flow from the wetwell to the drywell when the dFyWell is at a negative pressure with respect to the wetwell.
iherefore, wetwell-to-drywell vacuum breakers prevent an excessive negative differential pressure across the wetwell/drywell boundary.
Each vacuum breaker is a self actuating valve, similar to a check valve.
A negative differential pressure across the drywell wall is i
caused by rapid depressurization of the drywell.
Events that cause this rapid depressurization are cooling cycles, inadvertent drywel' spray actuation and steam condensation from sprays or subcooled water reflood of a break in the event of a primary system rupture.
Cooling cycles result in minor pressure transients in the drywell that occur slowly i
and are normally controlled by heating and ventilation equipment. Spray actuation or spill of subcooled water out of a break results in more significant pressure transients and becomes important in sizing the internal vacuum breakers.
In the event of a primary system rupture, steam condensation within the drywell results in the most severe pressure transient. Followingaprimarysystemrupture,pisiinthe drywell is purged into the wetwell free airspace,' leaving thc drywell full of steam. Subsequent condensation of the a
steam can be caused in two possible ways, namely, Emergency Core Ccoling System flow from a ruptured pipe, or containment spray actuation following a loss of coolant accident (LOCA). These two cases determine the maximum depressurization rate of the drywell.
j In addition, the waterleg in the vertical vents of the vent system is controlled by the drywell-to-wetwell differential j
pressure.
If the drywell pressure is less than the wetwell pressure, there will be an increase in the vent waterleg.
This will result in an increase in the water clearing j
i 1)
(continued)
ABWR TS B 3.6-37 10/18/93
Wetwell-to-Drywell Vacuum B 3.6.1.6 f
BASES i
i BACKGROUND inertia in the event of a postulated LOCA, resulting in an (continued) increase in the peak drywell pressure. This in turn will result in an increase in the pool swell dynamic loads. The internal vacuum breakers limit the height of the waterleg in the vent system during normal operation.
APPLICABLE Analytical methods and assumptions involving the SAFETY ANALYSES wetwell-to-drywell vacuum breakers are presented in i
Reference 1 as part of the accident response of the primary containment systems. The vacuum breakers are provided as-part of the primary containment to limit the negative differential pressure across the drywell and wetwell walls' i
that form part of the primary containment boundary.
The safety analyses assume that the internal vacuum breakers are closed initially and are fully open at a differential 2
pressure of 0.0352 Kg/cm d (0.5 psid) (Ref.1).
Additionally,1 of the 8 internal vacuum breakers are assumed to fail in a closed position (Ref. 1). The results of the analyses show that the design pressure is not exceeded even under the worst case accident scenario.
The vacuum breaker opening differential pressure and the requirement that all 8 vacuum breakers be OPERABLE are a t
result of the requirement placed on the vacuum breakers to limit the vent system waterleg height. Design Basis Accident (DBA) analyses require the vacuum breakers to be closed initially and to remain closed and leak tight, with thedrywellatahigher/pressurerelativetothewetwell.
The wetwell-to-drywell vacuum breakers satisfy Criterion 3 of the NRC Policy Statement.
LC0 All 8 of the vacuum breakers must be OPERABLE for opening.
f All wetwell-to-drywell vacuum breakers, however, are required to be closed (except during testing or when the vacuum breakers are performing the intended design function).
The vacuum breaker OPERABILITY requirement provides assurance that the drywell-to-wetwell negative differential pressure remains below the design value. The requirement that the vacuum breakers be closed ensures that there is no excessive bypass leakage should a LOCA occur.
l l
(continued)
ABWR TS
'B 3.6-38 10/18/93 I
Wetwell-to-Drywell Vacuum B 3.6.1.6 BASES i
APPLICABILITY In MODES 1, 2, and 3, a DBA could result in excessive negative differential pressure across the drywell wall, caused by the rapid depressurization of the drywell.
The event that results in the limiting rapid depressurization of the drywell is the primary system rupture that purges the drywell of gasiand fills the drywell free airspace with r
steam.
Subseqdent condensation of the steam would result in depressurization of the drywell. The limiting pressure and i
temperature of the primary system prior to a DBA occur in MODES 1, 2, and 3.
Also, inadvertant actuation of the drywell spray could result in rapid depressurization of the drywell. The vacuum breakers, therefore, are required to be OPERABLE in MODES 1, 2, and 3.
i In MODES 4 and 5, the probability and consequences of these j
events are reduced by the pressure and temperature limitations in these MODES; therefore, maintaining wetwell-to-drywell vacuum breakers OPERABLE is not required in MODE 4 or 5.
l ACTIONS A.1 With one of the required vacuum breakers inoperable for opening (e.g., the vacuum breaker is not open and_may,be.,
stuck closed or not within its opening differsntialJpressure
~
limit,sothatitwouldnotfunctionas" designed"dufiny"an
event that depressurized the drywell), the remaining seven OPERABLE vacuum breakers are capable of providing the vacuum relief function. However, overall system reliability is reduced because a single failure in one of the remaining vacuum breakers could result in an excessive wetwell-to-i' drywell differential pressure during a DBA.
Therefore, with one of the eight required vacuum breakers inoperable, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is allowed to restore et4 east--erwM the inoperable vacuum breakers to OPERABLE status so that plant conditions are consistent with those assumed for the design basis analysis.
The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is i
considered acceptable due to the low probability of an event in which the remaining vacuum breaker capability would not be adequate.
(continued)
ABWR TS B 3.6-39 10/18/93 6
i 1
Wetwell-to-Drywell Vacuum
]
B 3.6.1.6
~
BASES ACTIONS B.1 (continued)
An open vacuum breaker allows communication between the drywell and wetwell airspace, and, as a result,' there is the potential for wetwell overpressurization due to this bypass leakage if a LOCA were to occur.
Therefore, the open vacuum breaker must be closed. A short time is allowed to close the vacuum breaker due to the low probability of an event that would pressurize primary containment.
If vacuum breaker position indication is not reliable, an alternate method of verifying that the vacuum breakers are closed is we twel l ; p re's s u re; and Neri fyi hgl.th'atl ths;f p?ps id iabpvei t by. increasi ng Lthe.;dfyWell3Fsssurs;f by?015 re'ssure differentia wi tho u ty5k.lf d oe_sMotif aHj be } on0y3[p s i d i foril 5 fini;nn eup. The required 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Completion Time is considered adequate to perform this test.
C.1 and C.2 If the inoperable wetwell-to-drywell vacuum breaker cannot be closed or restored to OPERABLE status within the required Completion Time, the plant must be brought to a MODE in which the LC0 does not apply.
To achieve this status, the plant must be brought to at least MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and to MODE 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.
SURVEILLANCE SR 3.6.1.6.1 REQUIREMENTS e
Each vacuum breaker is verified closed (except when being tested in accordance with SR 3.6.1.6.2 or when performing its intended function) to ensure that this potential large bypass leakage path is not present. This Surveillance is performed by observing th.e_ vacuum breaker, position _.
indication or _ by lincreasings the;drywelli pressuretby;015_fpsid.
.abovef theWetwellfpressurerandiverifyingithatf the3 pressure differentialfdoes notlfalRbel.oK013;psid :foM1531nbtei witho'ut makeup. Tfie l'4' day Frequency is based on e ng i ne'eFi n g f j ndgme n t, b}sA kb rslaFe (ngnialgbiss ed @
is considered adequate in view of the fact?thst?theNacuUm; (continued)
ABWR TS B 3.6-40 10/18/93-3
5 i
- 1 Wetwell-to-Drywell Vacuum B 3.6.1.6 i
~ BASES S
SURVEILt.ANCE SR 3.6.1.6.1 (continued)
REQUIREMENTS (continued)~E J gravilfifdrces. This verification is also required within 2 g.
safety / relief valves or any operation that causes the drywell-to-wetwell differential pressure to be reduced by 2
2 0.007 Kg/cm d (0.1 psid). A footnote is added to provide additional assurance of closure if position indication i
instruments indicate one or more vacuum breakers are not closed.
SR 3.6.1.6.2 Each required vacuum breaker must be cycled to ensure that-it opens adequately to perform its design function and returns to the. fully closed position.
This ensures that the safety analysis assumptions are valid.
The 18 month Frequency of this SR is based on the need to perform the surveillance during an outage.
The vacuum breakers can only be manually actuated and are only accessible during an outage.
SR 3.6.1,6.3 Verification of the vacuum breaker opening pressure is necessary to ensure that the safety analysis assumption regardingvpcuumbreakerfullopendifferentialpressureof 0.035 Kg/cm g (0.5 psid) is valid. The 18 month Frequency is based on the need to perform this Surveillance under the conditions that apply during a plant outage and the potent 4al--fee-an-eeplanned transient-4f-the Surveillance
. vere pcefermed..ith the reacter at powce. Fee-t4 tis fecility, The 18 month Frequency has been shown to be js acceptable based on operating experience, and is furthed fest404ed-becau;c cf other surveillance; performed et sheeter-Frequeneies-that ccavey the pfcper fenet4ening states-fee-each-vac+um-heeakee the$asjiYe7disigfof3ths ia?uunG brsa ke rs.[ ( nof set ualtspWe qui redj fdQoperii ng ) ; ~ ' "
(continued) i ABWR TS B 3.6-41 10/18/93
' l a
= -.
~
2 1
i Wetwell-to-Drywell Vacuum B 3.6.1.6
]
i BASES l
SURVEILLANCE SR 3.6.1.6.3 REQUIREMENTS (continued)
A CHANNEL CAllBRATION is a complete check of the instrument loop and the sensor. The test verifies the channel responds to measured parameter with the necessary range and accuracy.
The 18 month frequency is based on the ABWR expected refueling interval and the need to perform this Surveillance under the conditions that apply during a plant outage.
HEFERENCE 1.
t t
8 I
i f
L l
ABWR TS B 3.6-42 10/18/93 i